Process and apparatus for finishing a magnetic slider

ABSTRACT

A process for finishing a disc drive slider in which a pressure generator applies multiple pressures to the back surface of one slider while the front surface of the one slider contacts a lapping surface to form a finished front surface of the slider. The slider is part of a substrate having multiple unfinished sliders formed in it. An etch process is used to etch trenches in the substrate aligned between the sliders and to form webs joining the sliders together. After the sliders are finished by lapping, the webs are removed to separate the sliders. The multiple sliders are conveniently held together during the finishing process and the etching process avoids damage to the sliders.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefits from U.S. ProvisionalApplication 60/218,262 titled “Stripe height control using independentcontrolled sliders and method to separate sliders from bars with deepreactive etching,” filed Jul. 13, 2000

FIELD OF THE INVENTION

The present invention relates generally to sliders for use in magneticstorage drives. In particular, this invention relates to methods andapparatus for finishing a disc drive slider that include lapping asurface of a disc drive slider.

BACKGROUND OF THE INVENTION

During the fabrication of magnetic heads for use in magnetic datastorage applications, an array of transducers and auxiliary circuits arefabricated on a common substrate in a deposition of metallic andnon-metallic layers. The array is then cut up into smaller bars, witheach bar including a row of multiple read/write heads. The bars are thenlapped to adjust an average stripe height (SH) of magnetoresistive (MR)transducers in the bar, the average throat height (TH) of inductivetransducer in the bar, or both. The auxiliary circuits in the bars areelectrical lap guides (ELGs) that sense the progress of the lappingprocess. Each electrical lap guide has an electrical resistance thatincreases as material is removed by lapping. Lapping is stoppedautomatically when the average stripe height and/or average throatheight are within acceptable limits. After the lapping process iscomplete, the bars are cut up into individual read/write heads orsliders using diamond saws.

The process of lapping a solid bar has a limited ability to adjust onlythe average stripe height or average throat height for all the slidersformed in the bar. There are remaining undesired variations inindividual stripe height or throat height among the sliders in a bar.

As higher recording densities are being introduced, there is a need forbetter control than this average control, particularly in the case ofstripe height. It is, however, inconvenient and expensive to handleindividual sliders in a lapping operation because of their small size.

A process and apparatus are needed that can handle bars of substratewith multiple sliders in each bar, while controlling lapping toindividually or independently control stripe height for each slider.

SUMMARY OF THE INVENTION

Disclosed is a process and apparatus for finishing a disc drive slider.The slider is part of a substrate bar having multiple unfinished slidersformed in it. An etch process is used to etch stress-isolating trenchesin the substrate aligned between the sliders and to form webs joiningthe sliders together. The apparatus includes a pressure generator thatapplies multiple pressures to the back surface of one individual sliderwhile the front surface of the one individual slider contacts a lappingsurface to form a finished front surface of the slider.

After the sliders are finished by lapping, the webs are removed toseparate the sliders. The webs flexibly hold the multiple sliderstogether in a fixture during the lapping process while allowing theindividual sliders to move independently. The pressures applied to eachindividual slider can be independently controlled, allowing for improvedcontrol of the stripe height (SH), the throat height (TH) or both ofeach sldier. The etching process avoids damage from the use of diamondsaws.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a disc drive.

FIG. 2 illustrates an unfinished substrate including multiple unfinisheddisc drive sliders.

FIG. 3 illustrates an unfinished substrate with a selective maskinglayer.

FIG. 4 illustrates an unfinished substrate with etched trenches.

FIG. 5 illustrates an unfinished slider with the selective masking layerremoved.

FIG. 6 schematically illustrates an apparatus applying multiplepressures to an unfinished slider during a lapping process.

FIG. 7 illustrates a finished substrate including finished sliders.

FIG. 8 illustrates a cross sectional view of a slider with an inductivetransducer and a layer including a magnetoresistive (MR) transducer.

FIG. 9 illustrates a cross sectional view that is transverse to the viewshown in FIG. 8 of the layer including a magnetoresistive transducer(MR).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the present invention, a bar of multiple disc drive sliders hastrenches etched between individual sliders using etching. The etching iscontrolled using a selective mask, and the etching is stopped before itcompletely cuts through the bar, leaving a web that keeps the slidersflexibly joined together for convenient handling during subsequentlapping operations. The use of etching avoids the use of diamond sawswhich can leave contamination in the form of chips and can also damagethe sliders.

A pressure generator applies multiple pressures to the back surface ofone individual slider while the front surface of the one individualslider contacts a lapping surface to form a finished front surface ofthe slider. The lapping can be automatically controlled by feedback fromelectric lap guides in the one slider being lapped. The slider beinglapped is able to respond independently to the pressures applied to itbecause the trenches provide stress isolation between the individualsliders. The webs flex to allow the slider being lapped to moveindependently of adjacent sliders.

After the sliders are individually finished by lapping, the webs areremoved to separate the sliders, preferably using masking and etching.

In FIG. 1, an embodiment of a disc drive 100 is illustrated. Disc drive100 includes a disc pack 126 having storage surfaces 106 that aretypically layers of magnetic material. The disc pack 126 includes astack of multiple discs and the read/write head assembly includes aread/write transducer or slider 110 for each stacked disc. Disc pack 126is spun or rotated as shown by arrow 107 to allow read/write headassembly 112 to access different rotational locations for data on thestorage surfaces 106 on the disc pack 126.

Read/write head assembly 112 is actuated to move radially, relative tothe disc pack 126, as shown by arrow 122 to access different radiallocations for data on the storage surfaces 106 of disc pack 126.Typically, the actuation of read/write head assembly 112 is provided bya voice coil motor 118. Voice coil motor 118 includes a rotor 116 thatpivots on axle 120 and an arm 114 that actuates the read/write headassembly 112. Disc drive 100 includes electronic circuitry 130 forcontrolling the operation of the disc drive and transferring data in andout of the disc drive.

FIG. 2 illustrates a substrate 20 in an unfinished condition includingmultiple unfinished disc drive sliders 22 arranged in a bar shape. Eachdisc drive slider 22 includes a front surface 24 which is lapped in asubsequent finishing process while pressure or force is applied to aback surface 26 (not visible in FIG. 2) of each slider 22. Each discdrive slider 22 is formed from a slider substrate and variousselectively deposited layers of materials that form a read/write headand electrical lap guides(s) in the deposited layers.

FIG. 3 illustrates the substrate 20 with a selective masking layer 26applied to the front surfaces 24 of the sliders 22. The masking layer 26is lithographically patterned to define masking grooves 28 which are notcovered by the masking layer 26. The masking layer 26 is formed of amaterial that is resistant to erosion by etching.

FIG. 4 illustrates the substrate 20 after deep trenches 32 have beenetched in substrate 20 using a microstructure etching process. Reactiveion etching (RIE), ion beam chemical dry etch, ion milling or otherknown microstructure etching (micromachining) techniques can be used.Etching processes are known, for example, from Handbook of Thin FilmTechnology, IOP Publishing Company 1997 (CD-ROM).

The position and size of trenches 32 are defined by the masking grooves28 and aligned between the individual sliders 22. A directional etchingprocess is preferred in etching trenches 32 in order to accuratelyreproduce the masking grooves and etch deep trenches 32. The substrate20 can be formed of a single crystal material such as doped silicon. Theetching process is stopped or controlled to etch trenches 32 onlypartially through the substrate 20, forming webs 34 that join thesliders 22 together. Webs 34 are thick enough to hold the sliders 22together during a subsequent lapping operation, and thin and flexibleenough to allow each slider 22 to mover responsive to pressure somewhatindependently of the adjacent sliders 22.

FIG. 5 illustrates the unfinished slider 20 with the selective maskinglayer 26 removed after the etching process is complete.

FIG. 6 schematically illustrates a process of applying multiplepressures 36 to an unfinished slider 22 during a lapping process. InFIG. 6, a portion of the substrate 20 of FIG. 5 is illustrated with thesame reference numerals being used in FIG. 6 that are used in FIG. 5.The bar-shaped substrate 20 made up of multiple unfinished sliders 22joined together by webs 34 is placed between a lapping surface 42 and amultiple pressure generator 38. Multiple pressure generator 38 generatesmultiple pressures 36 that are applied to the back side 26 of one of thesliders 22 as illustrated. Multiple pressures 36 can be eachindividually controlled based on electrical feedback 46 from anelectrical lap guide controller or circuit 44. Electrical lap guidecontroller 44 is connected to electrical lap guides (ELGs) 40 that aredisposed in the unfinished slider 22 that is being lapped. The frontsurface 24 of the slider 22 is in contact with lapping surface 42 whilecontrolled pressure is applied to back surface 26. A finished frontsurface is formed by lapping at front surface 24 based on feedback fromthe electrical lap guides (ELGs) 40. Feedback from the ELGs 40 controlsthe approach of the front surface 24 to the lapping surface 42. Theindividual pressures 36 can be adjusted in real time to change theprofile of pressure applied from front-to-back and left-to-right to varythe lapping rate in different regions of the front surface 24. Thestripe height (SH), the throat height (TH) or both of each individualslider 22 are precisely controlled using feedback from the electricallap guides 40. The electrical lap guides 40 are explained in more detailbelow in connection with FIG. 9.

The multiple sliders 22 can be lapped independently of one another. Thiscan be done sequentially with a single pressure generator 38. While thelapping is going on at one slider 22, the backsides of adjacent sliders22 can be held by a fixture 10 with openings 45 that subject adjacentsliders 22 to a vacuum to conveniently hold the bar-shaped substrate 20in place during the lapping operation.

Alternatively, the multiple sliders 22 can be lapped simultaneouslyusing multiple pressure generators 38 and multiple ELG controllers 44.When simultaneous lapping is done, the substrate 20 is held in place bymechanically engaging the webs 34 on an alternate mounting fixture witharms 12 inserted under the webs 34 as illustrated.

The webs 34 hold the sliders 22 together and each trench 32stress-isolates each slider 22 from an adjacent slider 22 during thelapping. The webs 34 hold the sliders 22 together while the trenches 32reduce transverse mechanical support of each slider 22 during thelapping.

After each of the sliders 22 in substrate 20 has been through thelapping process illustrated in FIG. 6, a finished substrate 20 asillustrated in FIG. 7 results.

FIG. 7 illustrates a finished substrate 20 including finished sliders 23that include a finished (lapped) front surface 25. The finishing of thesliders having been completed, the webs 34 are removed. Webs 34 can beremoved by etching as illustrated in dashed lines in FIG. 7.

FIG. 8 illustrates a partial cross sectional view of a slider 58 with aninductive write transducer 50 and a layer 66 including amagnetoresistive (MR) transducer and electrical lap guides (ELGs). Thecross sectional view in FIG. 8 is perpendicular to a bottom surface 60that is part of the lapped surface. The portion of the slider 58 that isillustrated is a portion near the trailing edge of the slider 58. Slider58 is formed on a substrate 52 in a conventional manner using thin filmprocessing techniques. The inductive transducer 50 includes an inductivetransducer throat 62 with a throat height 64. Lapping of surface 60 (asdescribed above in connection with FIG. 6) adjusts the height of theinductive throat 62 and also the height of a magnetoresistor andelectrical lap guides in layer 66. The arrangement of themagnetoresistor and electrical lap guides in layer 66 is explained inmore detail below in connection with FIG. 9.

FIG. 9 illustrates a cross sectional view that is transverse to the viewshown in FIG. 8 of the layer 66. Layer 66 includes a magnetoresistivetransducer (MR) 72 and electrical lap guides 70. As the bottom surface60 is lapped (as illustrated in FIG. 6), the stripe height 74 of themagnetoresistive transducer 72 changes, and also the electricalresistance of the electrical lap guides 70 changes as they are erodedaway by the lapping process. When the desired lap depth is acheived atdotted line 76 as indicated by lap guide resistances, the lappingprocess is stopped. The stripe height 74 is controlled by the appliedpressures during lapping as explained above in connection with FIG. 6.The throat height (TH) 64 is also controlled or adjusted by the appliedpressures during lapping.

In summary, a process for finishing a disc drive slider (22, 23) isdisclosed. A substrate (20) has multiple unfinished sliders (22) formedin it, each slider (22) has a front surface (25) and a back surfaces(26). An etch process is used to etch trenches (32) in the substrate(20), aligned between the sliders (22) and to form webs (34) joining thesliders (22) together. A multiple pressure generator (38) appliespressures (36) to the back surface (26) of one slider (22) while thefront surface (24) of the one slider (22) contacts a lapping surface(42) to form a finished front surface (25). The webs (34) are removed toseparate the finished disc drive sliders (26).

It is to be understood that even though numerous characteristics andadvantages of various embodiments of the invention have been set forthin the foregoing description, together with details of the structure andfunction of various embodiments of the invention, this disclosure isillustrative only, and changes may be made in detail, especially inmatters of structure and arrangement of parts within the principles ofthe present invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed. Forexample, the masking and etching may vary depending on the particularapplication for the slider while maintaining substantially the samefunctionality without departing from the scope and spirit of the presentinvention. In addition, although the preferred embodiment describedherein is directed to a slider for a disc drive, it will be appreciatedby those skilled in the art that the teachings of the present inventioncan be applied to other systems, like tape drive and magneto-opticaldrives, without departing from the scope and spirit of the presentinvention.

What is claimed is:
 1. A process for finishing a disc drive slider,comprising: A. providing a substrate having multiple unfinished slidersformed therein, each slider having front and back surfaces; B. using amicrostructure etch process to etch trenches in the substrate alignedbetween the sliders and to form webs joining the sliders together; C.applying multiple pressures from a multiple pressure generator to theback surface of one slider while the front surface of the one slidercontacts a lapping surface to form a finished front surface; and D.removing the webs.
 2. The process of claim 1 wherein the microstructureetch process comprises reactive ion etching.
 3. The process of claim 1wherein each slider includes an electrical lap guide (ELG), and E.providing feedback from the ELG on the one slider to the multiplepressure generator to control the approach of the front surface to thelapping surface.
 4. The process of claim 3 wherein each slider includesa magnetoresistive (MR) transducer with a stripe height (SH) and F.controlling the applied pressures to adjust the stripe height.
 5. Theprocess of claim 3 wherein each slider includes an inductive transducerwith a throat height (TH) and F. controlling the applied pressures toadjust the throat height (TH).
 6. The process of claim 1 wherein themultiple sliders are lapped independently of one another.
 7. The processof claim 6 wherein the multiple sliders are lapped sequentially.
 8. Theprocess of claim 6 wherein the multiple sliders are lappedsimultaneously.
 9. The process of claim 1 wherein the webs hold thesliders together and each trench stress-isolates each slider from anadjacent slider during the lapping.
 10. The process of claim 1 whereinthe webs hold the sliders together while the trenches reduce transversemechanical support of each slider during the lapping.
 11. The process ofclaim 1 where the grooves are defined by selective masking of thesubstrate.
 12. The process of claim 1 wherein the etching is directionaletching.
 13. The process of claim 1 wherein the webs are removed in stepD by reactive ion etching.
 14. The process of claim 13 wherein thesingle crystal material is doped silicon.
 15. The process of claim 1wherein the substrate is a single crystal material.